A Protemnodon skull from a cave at Mt. Cripps, northwest Tasmania.
Credit: Queen Victoria Museum and Art Gallery, Tasmania, Australia
SYDNEY: The fossilised teeth of a giant kangaroo from Tasmania may confirm once and for all that humans, and not climate change, pushed Australia's large prehistoric marsupials to extinction.
Australian and British researchers led by geochronologist Chris Turney, at the University of Exeter in England, have found new clues which may help settle the long-standing debate over how animals such as Thylacoleo, the marsupial lion, and the ground-sloth-like Palorchestes died out.
"This research… adds another important element, to an emerging global picture of the timing of the extinction of large animals," said co-author Tim Flannery from Macquarie University in Sydney.
Significant finds
In a paper published today in the U.S. journal Proceedings of the National Academy of Sciences, Turney's team report results of radiometric dating studies on fossil teeth showing that the giant wallaby-like marsupial Protemnodon Anac was still alive in Tasmania 41,000 years ago.
Co-author Richard Roberts from the University of Wollongong in New South Wales said that the fossils were dated in two ways; by carbon dating the bones as well as pollen samples lodged deep inside the long nose of the Protemnodon skulls.
Similar dates were found for the remains of six other ancient giant marsupial species from a total of four sites in Tasmania, including a cave found on Mount Cripps in the island's far north-west.
The finds are significant, because they show that these species, including the 120-kg Protemndon, were still present on the island when the humans arrived between 40,000 to 43,000 years ago. Previous studies had suggested that the animals died out earlier, before human habitation, which implicated climate change as the likely culprit for their extinctions.
Temporary land bridge
It had been thought that the giant animals went extinct in Tasmania at the same time as those animals on the mainland, which was around 40,000 years ago.
Geologists know that Tasmania was temporarily joined to the mainland via a land bridge which allowed humans to cross easily from 43,000 years ago until 40,000 years ago, when the sea engulfed it once more. Turney's team now shows that large marsupials lived in Tasmania for perhaps 2,000 years after humans arrived, and that they therefore lived alongside the earliest local Aborigines.
"Things were very climatically stable in that part of Australia and yet the mega-fauna still managed to go extinct," said Roberts. "So it's down to humans of one sort or another."
